FYI that little white plastic collar on the CV needle... I got mine off no problem. pushed down on it from the top with a small diameter wrench (bracing the needle's tip against the table). Put it back on then based on a walkthrough I read on here.

I've been unable to keep a steady idle without using throttle when stopped. When I messed with the mixture screw, leaning it out increased it to a healthy idle, but then my standard cruising throttle was severely lessened (excessive leanness?). It was shocking to see the mixture screw affect this wide range of throttle, but I'm still not totally comprehending it.

One question: To set idle on the CV carb, do I do it the same as I've read to do on other carbs? (reverse screw direction already taken into account). in other words, do I get it hot, then mess with the screw til it's idling as high as it'll go, then reduce the throttle screw until it's fairly low but maintaining a healthy idle, then increase it again via the mixture screw? (if it'll go any higher)?

Not exactly. When you're making your adjustments move the idle screw until the idles increases to it's "max" RPM in that range and then move the screw a 1/4-1/2 turn towards the rich side. If you leave it at that "high idle" point you will be running too lean.

Thanks to all for a great thread. I'm a newbie to the carb dissection...thinking of undertaking the process, but I may not have to at this moment. I'm running lean with a newly placed less restrictive filter/exhaust setup, getting slight hesitation from idle and some backfiring on deceleration. Great idle and acceleration otherwise. Other members have suggested increasing pilot/main, which I may well have to do, but could I start with the needle and mixture screw first? Iíve got AVL with BS29 stock. I was going to play today. In reference to the slide needle adjustment, raise to be RICH and lower to be LEAN. Correct? Also, is that with the carb still attached?

Mixture screw: clockwise lean; counter clockwise rich. Make sure the engine is nice a warm and set it up.

Needle: the richest setting on the needle is the lowest slot as you look down the needle. This is how you raise the needle in the carb.

Remember, the pilot jet, mixture screw and needle all work together between 0 and ~1/4 throttle. The main jet also plays a part and becomes more important as you work up the throttle. Most folks tend to start with the main jet first at WOT, then work their way down.

Logged

Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain2006 AVL Electra

If you pull the tank off you can get to the slide and needle without removing the carb. That's my preference. Others find it easier for them to leave the tank in place and remove the carb. Really it's personal choice; 6 of one, half a dozen of the other.

If you pull the tank off you can get to the slide and needle without removing the carb. That's my preference. Others find it easier for them to leave the tank in place and remove the carb. Really it's personal choice; 6 of one, half a dozen of the other.

I definitely prefer to pull the tank. Makes it a lot easier, plus Amals are notorious for warping when the flange bolts are over torqued, so I don't pull the carb off unless I'm doing a thorough cleaning.

If you've never opened up the carb before I recommend removing it and doing it on the kitchen table... well lit, clean, and no risk of dropping tiny parts on the ground. I tried to do stuff with it on the bike (first time ever) and it was WAAAAY easier to do it in the kitchen. (at least for the needle settings). Mixture screw and jets can be done with the carb on (and the tank on for that matter).

Still figuring out my own settings as we speak. Either way, I can pretty much guarantee you'll need a 17.5 pilot, and a larger main too (most people end up using the 120 size main). I'm on a 125 main right now but may be running a little rich. Like I said, more experimentation is coming my way...

So I've taken this BS29 apart and learned it well. Amazing to understand what the posts are referring to. I put in a 120 main from the 110 and raised the slide needle one shim. Pilot stock at 15. The bike would hardly keep idle, poor throttle response and needed choke wide open to stay alive, but minimal backfire, only right before return to to idle. Mixture screw did little to make a difference of helping idle.I changed 120 out to a 117.5 and raised the slide needle to highest point, with the white donut in place, plus shim(only has 3 notches). This resulted in less, mostly stable one or no pop backfire, but sluggish response to throttle overall and still idle wasn't super. So took slide needle back to middle, with the white donut in place and one shim. This resulted in great power and idle, but backfire increased again. I don't have a baffle in the Goldie exhaust, and I was going to add a 17.5 pilot dice the 120 main seems too rich. Thoughts on this config?

Sounds like you're making progress. The carb is fun to take apart, isn't it! I'm a constant tinkerer.

Anyway, I think your idle issue is related to the pilot jet, pilot circuit and / or the mixture screw. If the mixture screw was making no difference, then I'd suggest trying the 17.5. I tried a 15 pilot; it idles but was really anemic at any throttle point. At 17.5 and about 1/2 turn out, it idled nicely. That screw should make a difference.

Also, the crappy idle reminds me of an air leak in the air intake or the manifold forcing the whole system lean. I know it's another element, but its really important to make certain there is no air leak when tuning a carb. How to check? Spray wd40 over the hoses while running and see if you hear any difference in the idle. That Indian rubber does wear out.

Also make sure the pilot circuit in the carb body is not blocked which could be another reason the mixture screw makes no difference.

I'd stay with the 120 until your able to get to wide open throttle and do a few plug chops. I change between 117.5 and 120 depending on temp as I seem to be right on the edge between them. Every bullet is a bit different.

Sorry for the long rambling post! I'm too lazy to go back and edit it down.

Logged

Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain2006 AVL Electra

Thanks Dan. No worries; please ramble. Well, going on vacation for a week. Hate leaving a project sit, but will give time for the pilot to come in...and replacement baffle for that matter. In the meantime...dropping it off for new 4x19 tires front back for that beefier look. But that's another thread on its own.You all take care, keep the shiny side up, as they say.

Congrats on the tuning! I pulled mine apart again last night and shimmed up the needle. I have a tiny brass washer between the white plastic collar thingie and the needle clip (which itself is at the bottom [richest] setting).

It's a monster now. 17.5 pilot, Needle position as noted above, and I think I still have the 122.5 main in there. I'm loving it. I think i need to lean out my mixture screw a bit to keep a steady idle. Always a work in progress. Always.